1. Field of the Invention
The present invention relates to a power supply control apparatus with a power-saving mode, a power supply control method, and a power supply control software program.
2. Description of the Related Art
Devices having a power-saving mode have been known in the past. For instance, devices exist in which, in order to lower power consumption as much as possible in the power-saving mode, only the section detecting triggers for returning to the normal mode from the power-saving mode is energized and the supply of electric power to other sections is stopped.
On the other hand, as a reflection of the rising demand for power reduction in the power-saving mode, it is common to provide a switch on the commercial (external) power supply input side (called the “AC-side” below) to disconnect the circuit when stopping the supply of electric power to sections other than the trigger detecting section. The reason is that, in a situation wherein the AC side is connected to a power supply unit, power consumption within the power supply unit takes place when the output-side circuitry of the power supply unit is disconnected. For instance, a mechanical relay capable of handling large currents at low cost have been used as a switch for disconnecting AC-side electrical power (Japanese Patent Laid-Open No. 2004-157961).
On the other hand, with the advancement of communication technology, in devices connected to a network, there is an increase in the number of packets requiring response in a power-saving mode. It is conspicuous in situations, wherein the network includes numerous monitoring servers and client PCs sending out regular status request packets and the like generated by monitoring software, etc. For such packets, corresponding processing has to be performed by coming out of the power-saving mode. This creates the problem that the number of times the switch is tuned on and off increases and the life of the switch becomes shorter than the life of the device.
An effective method of prolonging the life of the switch consists in maintaining a standby state without transitioning to the power-saving mode from the normal mode for a fixed time period (e.g. 15 min) even if packet processing is completed within a shorter time. However, a problem existed in that power consumption increased in proportion to the delay in transition from the normal mode to the power-saving mode.